Thermal imaging is a sensing method for non-contact measurement of temperatures of thermally emissive objects. Thermal imaging devices detect radiation emitted by objects by sensing infrared photons and identifying the flux thereof. By using multiple sensing and focusing elements, the thermal photon flux from separate solid-angular fields of view can be obtained in a similar manner as visible-light cameras. As a result, an image of the temperature of objects being captured is generated.
Thermal imaging may be used to observe operating characteristics of electronic and/or mechanical equipment used in any number of industrial environments such as, for example, manufacturing, fabrication, and/or processing facilities. For example, localization of objects with heat contrast can assist in understanding or discerning the location of a conduit in a wall, a source of a water leak, or identifying faulty and/or overloaded circuit breakers. In these examples, a useful image interpretation may be straightforward such that an untrained or inexperienced user may perform it and discern the issue. In some examples, it is advantageous to enhance the interpretability of the images and perform a thorough analysis of the image and the underlying data in order to obtain a binary decision regarding the functional or structural integrity of an object or the determination of a quantitative figure relating to the functional or structural integrity thereof. As an example, in the field of window retrofitting for the purpose of increasing energy efficiency, an estimate of the insulation quality of a window is useful in order to determine the return on investment of a replacement window with a potentially higher insulation quality. In other examples, the determination of excessive current carried through a circuit breaker can identify a failed closed circuit breaker by determining the breaker rating through optical character recognition in a visible-light image, integrating the heat associated with the breaker, and using any number of approaches to calculate the estimated current carried through the breaker to obtain a binary measure of the breaker's integrity and/or a probabilistic estimate of the confidence of the measure. In both of these examples, the determinations are manually calculated and can be error-prone and time consuming.
Thermal imaging may also be incorporated into a predictive maintenance process used to determine the optimum time when equipment should be serviced and/or replaced. Excess heat given off by equipment is often a key indicator of excess wear or impending equipment failure, thus thermal imaging can serve an integral role in maintaining an efficient and productive work environment.
To perform a thermography scan, i.e., to obtain thermal images of thermally emissive objects, thermographers first identify all relevant unique objects and/or equipment, commonly referred to as “assets,” which may demonstrate an abnormal temperature-related issue. Thermal images are taken of each asset using a thermal camera while the thermographer adjusts for contrast and brightness, otherwise known as “level” and “span,” to set a mid-image temperature and temperature ranges in the image to optimize information presented therein. Setting appropriate level and span values is of particular importance because these values must appropriately surround meaningful temperature ranges in order to see and record abnormalities in thermal images. As an example, if the desired asset is an electrical panel, there may be a high temperature connection that exists under normal operating conditions. To ignore the high temperature connection, the top of the temperature range must be adjusted and saturated to allow for other subtle temperature variances to be seen. As another example, if an abnormally hot connection is identified, the thermographer may still wish to identify milder abnormally hot conditions. Accordingly, the level and span must be adjusted until any subtler issues become apparent. The thermographer can then record the image to be reviewed and analyzed. Thermographers will typically follow a designated route through the environment to sequentially capture images to allow for repeatability on later dates. During or after the process of obtaining images of all desired assets, the thermographer will review the images and ultimately identify areas of interest and/or concern.
Typically, this process must be repeated, e.g., every 6 months, to monitor areas of interest and/or identify any new areas of interest or concern. However, due to the specialized nature of industrial thermography, thermographers are again needed. Thermographers will thus periodically return to the environment, as needed, to re-perform their analysis. In doing so, they will follow a specified image capture route, created based on the initial thermography scan, that allows them to retrace their steps.
Nonetheless, it will be appreciated that using thermographers to obtain subsequent images to be analyzed can be prohibitively costly and time consuming. As an example, the environment (e.g., the manufacturing facility) may have to be shut down to perform the thermography scan and/or one or more employees may have to work with the thermographer to perform the scan.
Moreover, the acquisition of thermal images of the same scene at multiple times is typically associated with differences in the camera location and orientation (or camera “pose”). These differences in acquisition can result in images that do not match on a pixel-by-pixel basis, meaning one pixel does not refer to the same part of the scene or object within the scene in all images. It is possible to ensure a match across time points by fixing the camera in place, for example using a camera mount, or a tripod mount, that is located at a fixed location over time, such that the camera acquisition occurs at exactly the same location and orientation with respect to the scene at each time point. However, doing so is difficult because the orientation must be aligned exactly which is a time-consuming and error-prone process, and if the camera is left mounted at that location permanently, the camera is then unavailable to inspect other equipment and furthermore is susceptible to subtle shifts in pose over time.
Further, each scene to be monitored with repeated image acquisitions may be of a unique asset or part of asset, and therefore it may not be possible to differentiate between unique asset scans on the basis of the images themselves, which may lead to potential errors in misidentification of an image as referring to the wrong asset or part of asset. The proper analysis of thermal images when multiple scenes are present requires the correct association of a diagnostic thermal image with a scene. Each scene of an asset is typically unique, and when acquiring multiple scenes, it can be difficult to correctly identify the asset under investigation from a visual image alone, especially in the presence of multiple assets of the same type and appearance. Therefore, errors in scene identification can lead to failed diagnoses. To prevent this type of error, it is desired to uniquely identify each scene. In some cases it is possible to uniquely identify each scene using natural information from the image, such as the appearance of the asset and the background, and various methods for image matching may be useful, e.g. object recognition and template matching. However, in many cases natural scene information cannot be relied on because of an insufficient level of unique information, and in other cases, some of the natural scene information may change, e.g. due to dirt buildup, rust, movement of asset, and lighting changes.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the art will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary technical meaning as is accorded to such terms and expressions by persons skilled in the technical field as set forth above except where different specific meanings have otherwise been set forth herein.